The use of universal motors, including a field coil and a stator coil, to operate various tools is well known in the art. The field coil is excited with an electrical current from a power source, such as a typical electrical outlet. The field coil then rotates to induce an electrical current in the stator coil and provide the necessary power to operate the tool. Universal motors are typically attached to the tool housing by mount screws that are screwed through both the motor housing and the tool housing.
Permanent magnet D.C. motors are also known for use in operating tools. The permanent magnet D.C. motors include a field shell with a plurality of permanent magnets attached to the inside of the shell. Centered within the field shell is an armature core. A commutator is located outside of the field shell and is connected to a pair of coil windings that provide electrical current to the armature core to drive the armature. Once the armature has begun rotating, the polarity of the permanent magnets and the resultant magnetic field, drive the armature such that a shaft extending out of the field shell is driven, thus driving the power tool.
The permanent magnet motor assembly cannot be drilled for mounting screws because of its thickness, thus other methods and apparatus for attaching the field shell of these motors to the motor housing have been utilized. These methods and apparatus typically extend from the sides or the ends of the permanent magnet motors thus taking up valuable space. These methods and apparatus are also time consuming and expensive to manufacture.